Depends on how you charge and where.

If you charge at home, and you don't have a car tariff, it'll be ~25-30p per kwhr

If you get a car charging tariff then you'll be paying ~9p a kwhr.

if you are brave then you can use an agile prices which depends on the weather you can be paid to charge (my record was -11p a unit) however in winter it can be a lot high, like 45p a unit.

Charging on the street can be around 50p a kwhr up to 98p a kwhr